The present disclosure relates to an armature.
There exists rotating electric machines that include an armature that is formed with a core that is wound around by a coil and fitted by a shaft so as to be supported. The core is constructed by laminating, via integration, a plurality of ring-shaped plate materials that are each formed by punching a metallic plate material. The shaft is pressed into a shaft hole formed in the core so as to fix the shaft to the core. For the rotating electric machines, it is necessary to fix the shaft (to reach a strongly integrated state) to the core in a state where relative movement in the axial direction and in the direction around the axis is restricted (an integrating, fixing, and fastening state).
In order to achieve a strongly integrated state between the shaft and the core, an outside diameter of the shaft has been set to be larger than an inside diameter of the shaft hole so as to press the shaft into the shaft hole. Such a construction, however, has disadvantages. Not only is the press-in work difficult, but deformation also occurs in the core due to a press-in load that distorts the shape of the shaft hole. Shaft core accuracy of the shaft is thus impaired, and a crack also occurs in the core so as to deteriorate durability.
In order to resolve those problems, a proposed armature is constructed by forming projections (knurls) on an outer circumferential surface of a shaft and press-fitting so that the projections are caught in the inner circumferential surface of a shaft hole. This construction attempts to reach a state (a fastening state) that prevents rotation with respect to the shaft hole and restricts movement in an axial direction (see Japanese Published Unexamined Patent Application No. 2003-111326, for example).